One of the biggest strengths of open source languages is that the documentation is richly peppered with user-contributed comments, tips, and code snippets. The Java community is quite open sourcy in its own right, but the platform is, ultimately, controlled by one entity–and the documentation along with it.
Thankfully, lessons have been learned from awesome user-supplemented resources like the PHP Manual and Java has begun to spawn its own offerings in this area.
Lucas Chan, one of the developers here at SitePoint, has found KickJava useful. It’s a complete index of methods, classes, and packages in the standard Java platform libraries (J2SE, J2EE, J2ME, Java TV, Java Phone, and Java Card), containing user-contributed notes, tips and–more commonly–code snippets. If you’re an experienced developer that just needs to see a class in action to grasp how it works, this might be the ideal reference for you.
More recently, Javalobby (who also revamped their main site last week) have launched JDocs.com. A compilation of docs for 132 APIs as of this writing, the library allows users to submit comments for any class contained therein, and the whole thing is fully searchable. If you log in, you can even set up personalized lists of your favourite classes, packages, and APIs so the info you need is always a click away.
When JDocs.com was first launched there was a lot of static surrounding the fact that Sun didn’t want them to include the core Java libraries in the site. Sun was concerned that user-contributed comments interspersed with the official documentation could be confusing to developers and damaging to the integrity of the platform.
Thankfully, the brains at Javalobby were able to get Sun onboard by putting comments on these packages into a separate frame below the official documentation. And all is right with the world.